Generally, golf is a game that is played by striking a golf ball to a green to sink it into a hole-cup placed a certain distance apart from where the golf ball is struck, and golf is a record game, and thus, a golfer who sinks a golf ball into a hole-cup with the smallest number of strokes becomes a winner.
The most important things in golf are a distance of a shot and an accuracy of a shot. If a distance is good and a shot is accurate, the number of strokes may be reduced, and thus, every golfer practices for the distance of a shot and the accuracy of a shot.
However, even if a golfer know thoroughly knows a pose, which has to be maintained just before a swing and an impact so as to improve a distance of a shot and an accuracy of a shot, if a golfer does not correct a head-up habit by which a head of a golfer ascends before an impact, improvement of the distance of a shot and the accuracy of a shot is impossible.
This bad habit is seldom corrected, and it is impossible to keep a good score without correcting the bad habit.
This phenomenon occurs usually to a pro player as well as non-pro players (i.e., the general public), and thus, to avoid the bad habit, an intensive training for avoiding the head up is performed, and an assistive device for avoiding the head up or a device for a posture correction is used.
However, because there are many regulations which do not allow a golfer to use the assistive device during a golf round, the assistive device is not well used, and because the device for the posture correction used in a golf training cannot be used in a golf rounding, a golfer familiar to use the device sometimes does not get a good result.
Therefore, to improve a distance of a shot and an accuracy of a shot, a golfer has to repeatedly practice to correct the head-up habit.